CSA/maintenance type question

My friend is recently divorced and has 2 children living at home, age 17 and 8 (both at school). Her ex has offered £50 a week but she has no idea if he should be paying more or less on £25-£30k earnings.

I have advised her to got to the CAB but does anyone have a ballpark figure to suggest? He has a new partner who also works, she is alone and works (with tax credit top-ups so not earning loads).

She knows I'm asking and I will pass on any advice. I said MN would know.

If she goes on the CSA website there's a calculator on there to work it out.

He'll get a deduction depending on how many nights they spend with him. His new partner's income is irrelevant.

She might want to weigh up that the CSA are notorious for not getting it right, and if he's reliable and offering to pay without going through them she might be better off. Using the calculator would give her an idea of how much to negotiate with him.

I suspect he should be paying more. My XP was on £22k at the start of the year and the CSA website said he should pay £300 a month for a baby and toddler, calculations might be different for babies though.